Ring manufacture, productive of face contact seal

ABSTRACT

Methods, apparatus, and improved structure having as their common basis the sequence of collapsing a piston ring in a fixture approximating engine bore diameter, and separately lapping a major portion of the ring side and a remaining locality of the side of the ring while it is so collapsed, until circumferentially continuous portions of the side are flat in the range of at least about 10 to five light bands. The broadest method disclosed is the use exclusively of rings so carefully made and so lap inspected as above on a percentage basis that the major portion of the side has all points thereon in coplanarity and the remaining locality has all points thereon in coplanarity, all to a degree equivalent to the stated range to seal in respective full face contact and full line contact.

United States Patent 1 1 Packard et al.

[ 1 Jan. 28, 1975 1 1 RING MANUFACTURE, PRODUCTIVE OF FACE CONTACT SEAL[75] Inventors: Norman M. Packard, Des Plaines;

I John W. Gaines, Wheaton, both of [211 App]. No.: 382,787.

Related U.S. Application Data [62] Division of Ser. No. 195,955, Nov. 5,1971,

abandoned.

[52] U.S. Cl..... 29/l56.4 R, 29/1565 R, 29/156.63, 51/290, 51/324,277/216 [51] Int. Cl B23p 15/00, B23p 15/08 [58] Field of Search29/1566, 156.63, 156.4 R, 29/1565 R, 222; 51/290, 324; 277/216, 170,

3,751,784 8/1973 Packard 29/1566 FOREIGN PATENTS OR APPLICATIONS 849,1309/1960 Great Britain 277/216 Primary Examiner-C. W. Lanham AssistantExaminerDan C. Crane Attorney, Agent, or Firm-John W. Gaines; Floyd B.Harman 1 1 ABSTRACT Methods, apparatus, and improved structure having astheir common basis the sequence of collapsing a piston ring in a fixtureapproximating engine bore diameter, and separately lapping a majorportion of the ring side and a remaining locality of the side of thering while it is so collapsed, until circumferentially continuousportions of the side are flat in the range of at least about 10 to fivelight bands. The broadest method disclosed is the use exclusively ofrings so 173 carefully made and so lap inspected as above on apercentage basis that the major portion of the side has all [56]References Cited points thereon in coplanarity and the remaining local-UNITED STATES PATENTS ity has all points thereon in coplanarity, all toa degree 1,780,003 10 1930 Chance 29/l56.63 g g range Seal respecwe2,654,977 10/1953 Squibb et al.. 29/1566 ace Contact u Contact Zucker 4D awin F- r 3,073,689 H1963 Kupfert et a1 51/324 g es FIRING A/ 30PRESSURE PATENIED W 3.862.480

SHEET 1 BF 5 2 FIRING PATENTED 3,862,480

SHEET 0F 5 l Hf/JV) LAP/PING PRL'SSURE 46' Y FIR/N6 PRESSURE I i 1 RINGMANUFACTURE, PRODUCTIVE OF FACE CONTACT SEAL This is a division ofapplication Ser. No. 195,955, filed Nov. 5, 1971.

This application relates to subject matter of the type generally asshown in US. Pat. No. 3,587,155, owned by the same assignee.

Our inventions relate to ring manufacture productive of face contactseal. More specifically, they relate to manufacture of a piston ring,received in the compression ring groove of an I.C.E. piston andproductive of substantially absolute face contact in the side seal madewith the groove.

Blowby presents a problem in production piston engines. The need, as weenvision it, is to control blowby so that in production we are capableboth of making it predictable and of keeping it at a uniform, desirablylow value from engine to engine, at least in precision made productionengines which, in general, are of the multicylinder type.

Blowby emissions are one of the more obvious air pollutantsbecauseseveral of the polluting constituents thereof are clearly visibleas emitted.

Blowby is one of the factors effecting lubricating oil control. Solvingthe blowby problem will have a material influence on reducing engine oilconsumption, and we have discovered that the key to the solution is inthe compression rings on the pistons.

According to our inventions, the engines are sealed, i.e., each pistonand its surrounding cylinder wall are mutually sealed by an interposedpiston ring either so carefully made or so lap inspected on a percentagebasis that one and preferably two conditions obtain. One condition,desirable though not necessarily essential, is that the local innerperipheral edge of the ring at the groove sealing side thereof iscopolanar at all points or else so localizedly lapped, in a narrow bandalong the inner peripheral edge at the side, that the ring will seal theconfronting side of a receiving groove in a narrow, substantiallycontinuous ring of pressure contact which amounts to line contact or, atmost, is very narrow at the widest points. The resulting narrow if notline width ring at the side of the piston ring makes up only a minorportion of the overall side. The one condition which is essential isthat at least the major portion of the groove sealing side of the ringis coplanar at all points or else so lapped overall, in a wide face sealarea, that the ring will seal the confronting side of the receivinggroove in a circumferentially uninterrupted ring of face contact. Theoverall side of the ring which seals the groove side as aforesaid forms,for its major portion as viewed in cross section, a slight obtuse angleto the groove side and also to, if present, the lapped peripherallocality. Or, viewed in cross section the other way when the ring is infree spring state, the lapped peripheral locality, if any, is aninternal frusto cone forming an obtuse angle with the remaining majorportion of the side of the ring which is flat.

The disparity in the angularity between the mutually confronting sealedand sealing sides of the respective receiving groove and piston ring isdeliberate, and under pressure during compression and firing in theengine cylinder the ring deflects into what amounts to face contact withthe groove side over at least the major portion of the side of the ring,thus multiplying to substantial proportions the sealing area at thecritical time. So sealing with narrow band contact and line contact orsealing with face contact, depending upon the presence or absence ofhigh pressure conditions. complement one another to reduce the blowby,i.e., escape of firing pressure into the crankcase by leakage in thecylinders past the pistons.

Our inventions thus materially reduce or substantially eliminate theproblem of unpredictability and largely uncontrollably high magnitude ofblowby, as will now be explained in detail. Features. objects, andadvantages will either be specifically pointed out or become apparentwhen, for a better understanding of the inventions, reference is made tothe following description taken in conjunction with the accompanyingdrawings which show certain preferred embodiments thereof and in which:

FIG. 1 is a longitudinal elevational view of a portion of a piston andcylinder in an engine embodying one of the present ringinventions, theembodiment of FIG. 1 being shown in one of its operating positions incollapsed state;

FIG. 2 is similar, but with the embodiment of FIG. I shown in anotheroperating position in collapsed state;

FIG. 3 shows the embodiment of FIG. 1, in the operating position incollapsed state of FIG. 2, but with the environment being a lappingfixture to witness the ring for inspection purposes;

FIGS. 4 and 5 are enlarged fragmentary views corresponding to FIG. 3,showing the ring in respective major portion lapping and remaininglocality lapping positions;

FIG. 6 is an isometric view of the ring bottom side, which is thesealing side, at outset of witnessing the major portion;

FIG. 7 is a face view of the ring bottom side, which is the sealingside, following double angle lap witnessing;

FIG. 8 is a view similar to FIG. 5, but showing a modification of ourinvention;

FIG. 9 is a view similar to FIG. 8 but showing a further modification inring-open position;

FIG. 10 is a view similar to FIG. 4, but showing another modification;

FIG. 11 is an enlarged fragmentary view corresponding to FIG. 2, butshowing a further embodiment of the invention;

FIG. 12 is an enlarged fragmentary view similar to FIG. 1, but showing afurther modification; and

FIGS. 13 and 14 are enlarged fragmentary views similar to respectiveviews 2 and 4, but showing the FIG. 12 modification of our invention.

Qur inventions about to be particularly described apply to, amongothers, rectangular positive torsion ring structure, half keystonepositive torsion ring structure, and rectangular and half keystonenegative torsion or reverse dish ring structure. Slightlyoversimplitied, a positive torsion rectangular ring is basically onewhich is twisted in a ring groove of rectangular cross section with thelower side of the ring bearing against the bottom of the groove at theradially inner part of the groove and inclining upwardly and outwardlytherefrom. A positive torsion half keystone ring is along the same linesas above but is wedge tapered along the upper side, and the groove topis complementarily tapered to conform with the wedge shape of the halfkeystone ring. Finally, the negative torsion rectangular ring twists ina rectangular groove whereby what the ring does is to have the upperside of the ring bear against the top of the ring groove in the innerpart of the groove, slanting downwardly and outwardly therefrom, or elsewhat the ring does is to have the lower side of the ring bear againstthe bottom of the ring groove in the outer part of the groove. incliningupwardly and inwardly therefrom, or else the ring sometimes does both.

All of the rings concerned are the so-called split rings, having aparting located at some point around the circular length of the ring.Each such ring is compressed from its normal relaxed or free state bymeans of a ring compressor so that it assumes a collapsed state with theparting closed or substantially so. ln reaching the collapsed state, therectangular torsion ring. for example, twists or distorts or dishes outof its normal plane in well known way dependent upon whether the curvedinner face at the back of the ring has been selectively undercut at oneside or the other of the ring. When collapsing, the rectangular torsionring always takes a dished position with the undercut portion occupyingwhat becomes the concave or internal frusto conical side of the dish.

The metal of the foregoing rings is usually alloyed cast iron or ductilecast iron, and the pistons are cast iron or an aluminum alloy. Pistonsin the latter category have the compression ring grooves formed eitherdirectly in the aluminum or in hardened, grooved inserts carried by thealuminum piston.

Against this background, it is believed that FIGS. 1, 2, and 3 showingone preferred embodiment of our ring invention can be readilyunderstood.

LOCALlZED SEATED OPERATION, COLLAPSED STATE FIG. 1

A rectangular positive torsion ring is shown in that one of itsoperating positions in an engine in which the ring locally seats at thefrusto conical side with the inside diameter corner thereof, i.e., withthe ring being lD seated, as that eventuality will be hereinafterreferred to. When the ring is [D seated, a narrow width ring 22 ofpressure contact on the ID establishes at least continuous lineengagement with the inner portion of the confronting bottom 24 of arectangular ring groove 26 in an engine piston 28. The pistonreciprocates internally along the wall 30 of a cylinder of amulticylinder engine 32, being sealed to the wall by the ring 20. Thering 20 is a compression ring, and is illustrated in the top or firstring position on the piston although the design is fully effective asthe second, third, etc., compression ring on a multiringed piston.

The adjacent ends of the ring defining the parting indicated at 34 arepractically touching at the operatinng temperature of the ring, but ineach engine the designer always takes care to keep them from actuallybottoming against one another because of the danger that the ring mightseize in the cylinder. The ring is thus a live ring, functioning at alltimes as a cast iron spring preloaded so as to press outwardly againstthe cylinder wall.

In the collapsed operating state in the groove as shown in FIG. 1, thering 20 has a twisted position, due to its inherent torsion, during thesuccessive exhaust and suction strokes of the piston 28. The slightacute face angle, which the essentially cylindrical face 36 of the ringmakes with the vertical, accounts for a unidirectional oil pumpingaction produced by the ring.

During the exhaust strokes referred to each of which is in the outward(up) direction, the ring provides good oil control, keeping an oil filmon the hone pattern in the wall 30 at a sufficient but minimum thicknessfor lubricating purposes. Actually, the narrow wedge of oil beingencountered by the ring exerts hydraulic face pressure, causing a slightradial inward collapse of the ring 20, and preventing it from trappingand pumping the oil upward on the cylinder wall while the ring is somoving upward. During each suction stroke, which is inward, the ring 20due to the scraping action of the bottom corner of the face 36 thereofcollects the oil in the inward (down) direction and forces it downwardlyahead of the ring. The ring does so because there is no longer anyhydraulic pressure on the ring face pushing it away from the cylinderwall. The oil cannot readily escape from the groove 26 because ofcontact between the ring and the top ofthe groove 26, and thus a bottomor face sealing side 38 of the ring pushes the oil downward.

FULLY SEATED OPERATION, CQLLAPSED STATE FIG. 2

During the successive compression and firing strokes of the piston 28, alocalized sealing engagement effected by pressure contact of the sealring always insures as a first stage of sealing that no appreciablepressure dissipation can take place by leakage past the ring 20. Hencethe ring is susceptible to be flattened by the ensuing buildup ofpressure. So, by a second stage of sealing, the bottom side 38 of thering is forced into a fully seated ring area of face seal contact, i.e..with the bottom side FS seated, as that eventuality will be hereinafterreferred to, against the major portion of the confronting bottom 24 ofthe ring groove 26. In other words, the ring reacts to the pressure byuntwisting about the ID corner 22 and the inner portion of the groovebottom as a fulcrum.

The trapped pressure produces a consequent downward and outward forceagainst the respective flat upper side 40 and curved rear side 42 at theback of the ring. Hence, the curved face 36 at its lower corner is bothspring loaded mechanically and pressure loaded by gas into essentiallyleak-free contact with the cylin der wall 30.

Flatness is essential in the sealing side 38 if effective dynamic facesealing is to be realized. At or near top dead center, the piston 28rocks or shifts from its broken line position 28a in FIG. 2. Theantithrust side 35 of the piston is withdrawn from the side of thecylinder wall and the thrust side 37 is forced against the opposite sideof the cylinder wall as the piston takes the broken line position 28b onits downstroke in the bore. Because the ring 20 stays centered in thebore, there is appreciable sliding motion between the ring bottom side38 and the groove bottom 24 across their interface. which mustnevertheless maintain the face seal.

When the ring 20 is FS seated as a result of firing pressure holding thebottom side 38 flat against the bottom 24 of the groove, effectivesealing is insured because the flatness of the major portion of the side38 is preferably in the range of at least about 10 to five light bands.No greater approach has been found necessary to perfect flatness of theface seal in order to achieve the practical control of blowby desired,although two light bands would, for example. improve the operation atleast theoretically.

Anyway, the precise range of flatness is not the matter of basicimportance here involved, but rather it is systematic analysis andinsurance in all cases of good face sealing contact.

NORMAL RELAXED OR FREE SPRING STATE FIG. 3

In the free springstate of the ring having a fully expanded diameter asshown by the broken lines 2011 in FIG. 3, the adjacent ends of the ringmove to their fully withdrawn position so that they are partedconsiderably at 34. It is when the spring is unloaded and in free state,during the ring manufacturing process, that the respective upper andlower sides 40 and 38 are made flat and parallel, and the side 38 ispreferably lapped in a lapping fixture to within the range of ten tofive light bands or to greater flatness, such as to two light bandsflat. Hence, the bottom sides 38 of the ring presents a fairly precisesurface.

In order to make the ring twist because of its cross section, the curvedrear side or back 42 (FIGS. 2 and 5) is relieved by an undercut adjacentthe top side 40 only, as by a chamfer or, as actually illustrated, by arabbet or counterbore 44. So there is definite asymmetry in the crosssection whereby, when the parting in the ring is closed, the ring dishesinto an upwardly concave collapsed form (FIG. 5).

RING CONTROL The manufactured ring according to our objective hasplanarity on at least the major portion of the sealing side, when FSseated, to at least about 10 to five light bands of flatness asmanufactured.

It is now within the skill of the art, with careful control in ringmanufacture over such variables as metallurgy, temperatures,manufacturing procedure, tempering, and details of ring design such ascross section and the like, to materially increase the proportion ofrings in a production run above what could be expected as thehappenstance or random group having face seal flatness when the ring isFS seated. So through careful control of the manufacturing process andother variables, the deliberate increasing of the proportions of suchrings in the run can be realized to an expectancy of 50% and better,perhaps upwards of 90% or 95%, or possibly of 98%, which will have whatcan be stated as the coplanarity inherency in the face sealing side ofthe ring when flattened while in its collapsed state. Stated anotherway, at least the major portion of the sealing side of the ring in eachcase will, when flattened while collapsed, be uniplanar.

In such case, the product becomes not the happenstance or exception butthe rule, and what essentially amounts to absolute area sealing, i.e.,uninterrupted face contact side sealing along the full width of theinterface, can be achieved with the ring.

Obviously, a selection-rejection process must be used for witnessing theface sealing face at least to the extent ofa spot-check inspection.Although possible, it sounds somewhat idealistic to expect to achieverings which to a 100% extent have major portions oneach of which thelocus of all points will fall in one plane when the ring is FS seated.Practical manufacturing does not allow absolute predictability, andcertainly the manufacture of positive torsion rings which must bemechanically distorted to install them and gas distorted to flatten themfollowing installation does not allow absolute predictability.

The ring of FIGS. 4 and'8 can be viewed as such a ring havingsubstantially absolute coplanarity along the major portion of thesealing side when mechanically and gas distorted as described, and itwill be understood that the parting at 34 (FIG. 2) although greatlyexaggerated corresponds to the operative parting or split or gap in thering in collapsed state in the FS seated position.

The spot-check inspection. referred to, of such production rings is nodestructive test, and a ring to be so tested is merely lapped a few teststrokes to the point where the resulting uninterrupted flat face sealsurface can be perceived visually. Rings which pass the test when sowitnessed are perefectly usable in engines, whereas the rings sowitnessed which do not pass the flatness test become rejects. In otherwords, a reject having one or more high spots or one or more low spotspreventing it from passing the visial inspection flatness test would, ifsalvage or patching were attempted, require the removal of too muchmetal by lapping to be acceptable thereafter. In other words, a ring isdesigned for certain characteristics obtainable with a particular volumeof metal, and removal of so much metal by lapping would lighten the ringand destroy certain characteristics preventive of the basic designobjectives from being realized.

LAP APPARATUS FOR WITNESSING FIG. 3

An aspect of novelty is believed to reside in the fact that, prior toour discovery of the realities of the matter, there hadbeen and neverwas any basis for accepting as a foregone conclusion that a positivetorsion ring, flat on the bottom side in free state, would so uniformlydistort into its pressure flattened collapsed state as to establishuniplanar face sealing contact with a groove side which was to be facesealed thereby and which was planar or substantially so. Prior to ourdiscovery, it was never appreciated and yet, as a general rule, theusual production-made positive torsion ring when FS seated tended to benoncoplanar along the major portion of its sealing side which presenteda succession of high spots and low spots, somewhat according to a wavyor undulating pattern. Hence, there existed no fundamentally orderly andsystematic way whereby the engine designer or assembler could predictthe amount of blowby which would be produced by each new engine asfinally built.

So as to witness on a percentage basis the actual condition during aproduction run of torsion rings, a chuck or fixture 46 holds the ring 20with the sealing side 38 thereof depending and exposed by protruding inthe range of about 0.010 inch to 0.015 inch in the ID seated state. Thering-receiving mouth 48 of the fixture has identical diameter to thecylinder bore size of the engine in which the ring is to be installed.

The lap apparatus includes a raised annular confronting lap surface 50against which the ring 20 is pressed by any suitable mechanism, such asfor example, a drill press which supports the fixture 46 through a stem52.

Appreciable downward pressure is exerted on the stem 52 by a large aircylinder 54, and rotary motion is imparted to the mechanism so as torotate the stem 52 in the direction indicated by an arrow in FIG. 3.Such pressure and rotary motion, as a result of the friction between thering 20 and raised lap surface 50, im-

part rotary motion in the direction indicated by an arrow to the table56 supporting the surface 50. The table 56 is circular and the lapsurface 50 revolves about a spindle 58 rotatably supporting the table 56above a fixed trough structure 60'. Lapping compound is usually used.

A full 360 lap results because of the ring rotating relative to the lapsurface revolving thereunder. The lap surface 50 displays the usualundistorted mirror flatness. In some cases a table drive, not shown, canbe used to advantage, particularly if iniform, positive drive motion ofthe table is desired about its spindle 58.

DOUBLE ANGLE LAP, FIRST STAGE FIG. 4

With the ring in its unparted or collapsed state, heavy air pressureforce exerted through the fixture 46 untwists the ring 20 into FS seatedstate, deflected toward flat face-to-face contact with the precision lapsurface. A brief lapping period ensures.

DOUBLE ANGLE LAPPING, SECOND STAGE FIG. 5

Suitable air pressure reduction to a light air pressure force exertedthrough the fixture 46 enables the ring 20 to twist itself under its owntorsion into ID seated state, with the protruding inner periphery 22 incontact with and the major portion of the side 38 forming a slight angleto the lap surface 50. A second stage of lapping ensues, which is againfor a brief period.

REJECTION FIG. 6

If high spots or low spots are witnessed during lapping, the ring 20becomes a reject. Such a ring is shown in FIG. 6, whereafter the firststage of lapping discloses one or more high spots 60 on the majorportion of the sealing side 38 of the ring.

As previously indicated, it is not believed economically sound and it iscertainly not desirable to continue the lapping until all high spots andlow spots disappear. Time will be required, coarse and fine lappingcompound will be required, and as indicated certain characteristics ofthe ring will be altered with the weight of metal removed. The ring 20shown in FIG. 6 is shown in its FS seated, collapsed state.

SELECTION FIG. 7

The ring 20 is in free spring state as shown, and shown with itsprojecting inner periphery 22 presenting a lapped narrow sealing band atthe corner which forms an angle of intersection with the major portionof the side 38. The band is very narrow, indicative of coplanarity ofthe periphery prior to lapping, and the band widens slightly at 62adjacent the gap 34, shown open. The reason is that the gap-forming endportions of the ring 20 do not undergo maximum twist, such as, forexample, does the ungapped portion of the ring 20 diametric thereto.

So for all practical purposes, the lapped inner periphery 22 is a narrowinternal frusto cone which will be flat to at least about light bandswith the ring lD seated. The innner periphery 22 thus for all practicalpurposes is coplanar at all points, insuring positive first stagesealing.

The major portion of the sealing side 38 makes up the remainder notencroached upon by the lapped narrow sealing band on the periphery 22.When the ring is in the FS seated, collapsed state, the major portion ofthe side 38 has a lapped flatness of at least about 10 light bands. Sofor all practical purposes, it will be coplanar for positive facesealing under the engine pressures up to and including peak firingpressure. insuring the positive second stage sealing.

The ring shown in FIG. 7 will be a selected ring and will be used inengines with the other selected rings and with the noninspected rings.The latter rings will obviously have a single sealing angle, unlapped,in contrast to the double angle lap surface of selected witnessed ringsof this embodiment.

The stage of lapping the ring when ID seated is not always essential,and the operation can be altogether eliminated, as in the example now tobe described.

SINGLE ANGLE LAP FIG. 8

In this example, the ring 20 is selected after the sealing side 38 hasbeen successfully lapped and witnessed in the FS seated, collapsedstate, deflected toward flat face-to-face contact with the lap surface.With release of heavy lapping pressure, the ring takes the positionshown in solid lines in FIG. 8 and is removed from the fixture 46 andput into use.

The ring 20 is selected because, as witnessed, it will have anequivalent flatness to at least about 10 to five light bands when in theFS seated, collapsed state. And first stage sealing, in the ID seated,collapsed state, can now be conclusively presumed.

In other words, ring control during manufacture is presently within theskill of the art to insure that, with face flatness known to exist onthe face sealing side, it is a necessary attendant therewith that theinner pe riphery 22 thereof will have all points uniplanar when IDseated, to an equivalency of at least about 10 light bands flatness.Therefore, two stage sealing will result with the line contact at 22being multiplied by face contact at 38 during the second stage ofsealing. The periphery indicated at 22 as viewed in cross section isessentially a knife edge.

The angles involved in the illustrated embodiments of our inventions aresmall and the showings have required great exaggeration in order for theangles to be manifest at all. In what amounts to the ID seated,collapses state of the ring 20 shown in FIG. 8, the residual torsionexpends itself when it twists the ring in the ring roove, not shown,only to the extent that the botton corner 64 of the ring face 36 isabout 0.00l inch higher than the inner peripheral edge 22 of the sealingside 38. Thus, the frusto conicity, in a ring of nominal bore size 4.3inches for example, forms an acute angle in the range of about /2 to 3.

Similarly, when the ring 20 is in FS seated, collapsed state, not shown,the ring face 36 is at an acute vertical angle in the range of about 1to 3. Thus, the angles formed with the respective bottom of the ringgroove and cylinder wall, though extremely minor, are critical.

The single angle lapped (i.e., inspected by witnessing and selected) andthe single angle unlapped (noninspected) rings exhibit a novel andimportant feature of the inventions in terms of wear-in, compared toprior rings. Inasmuch as the side scaling is right in the firstinstance, no run-in or wear-in is necessary as with the prior art rings,which in some cases are eventually worn in to effect proper two stageside sealing and which in other cases never wear-in to effect proper twostage side sealing.

There is another feature which is important and which it now is believedwill be readily apparent. Operation of an engine equipped with thesingle rings not only does not proceed on a hit or miss basis for sidesealing as with the prior art rings, but rather proceeds whereby thering-receiving groove laps the single angle knife edge in service so asto seal in narrow band contact. and laps the seated face seal so as toretain it flat in service.

It therefore becomes apparent. it is believed, how the same twoimportant features have further application in the respect ofeliminating need for wear-in in the first instance, and in the respectof not impairing the integrity of the initially proper side sealing withwear, in service. As applied to double angle lapped rings (FIGS. 1, 2,3, 5, 7, 10, 11), the ringreceiving groove laps the lapped seated faceseal so as to retain it flat in service and laps the lapped inner localband at the ID corner so as to retain it flat in service.

Hence, freedom from blowby pollution of the air is not only insured inthe first instance with a new engine, but as a continuing thing as theengine becomes worn.

BLUNTED EDGE FIG. 9

Because of the effective knife edge formed where the inner periphery 22intersects the backside 42 of the ring, it is preferable to uniformlyblunt the ID corner with a very small chanfer or bevel 66. Otherwise,the sharpness of the ring as it twists and also moves laterally of thering groove can do damage by cutting or gouging the metal in the groovebottom.

For simplicity, however, the chamfer 66 does not appear in most of theshowings of the rings hereof.

DOUBLE ANGLE LAP, IN INVERSE STAGES FIG. 10

If the ID corner lap is desired to be included rather than eliminated,the double angle lap can be performed in an inverse order of stages fromthe preceding embodiment given. Thus if preferred for the results ofFIG. 10, the localized lap with the inner periphery 22 under lightlapping pressure can be performed first. Then as a second stage, theremaining major portion of the sealing side 38 can undergo lapping underheavy lapping pressure as illustrated in FIG. 10.

HALF KEYSTONE RING FIG. 11

The inventions readily apply to other positive torsion rings, when nadeand installed as above. In this example, a half keystone ring 120 isuntwisted by the gas from its torsionally twisted state into the FSseated position as illustrated in solid lines in FIG. 11.

Under firing pressure when the ring is in the illustrated FS seated,collapsed state, the major portion of the sealing side 138 is flatagainst the groove bottom 124. The remaining lapped locality 122 is atthe inner periphery, and a dulling chamfer is provided on the corner at166.

The ring 120 has a ring face 136 disposed at an acute vertical angle anda tapered upper side 140. The complementarily tapered top ofthe grooveis frusto conical.

NEGATIVE TORSION RING FIGS. 12, 13

A rectangular negative torsion ring 220 according to this example has anupper side 240 and a sealing or lower side 238. In free spring state,not shown, the sides 240 and 238 are parallel horizontal upper and lowersides, similarly to the embodiments of rectangular rings previouslydescribed.

Also in similar manner, the negative torsion ring 220 has a face 236forming an acute vertical angle for oil control purposes described.extending upwardly and inwardly. Distinctively, however, the ring 220has a curved back 242 arranged as an inner curved side with an annularportion 244 locally removed in the down direction, not up direction asheretofore illustrated. The result is that when the parting in the ringis closed to put the ring in the ID seated. collapsed state as shown inFIG. 12, the upper and lower sides 240 and 238 incline inwardly at asmall acute angle to the horizontal and in the up direction (not downdirection as heretofore illustrated).

Further distinctively, the ring 220 reacts under firing pressure byuntwisting about the outer edge 224 of the groove bottom as a fulcrum.The single angle bottom side 38 in this manner takes the FS seated,collapsed state, deflected toward the flat face-to-face contact to sealagainst escape of the firing pressure.

SINGLE ANGLE LAP, NEGATIVE FIG. 14

The negative torsion rings 220 are inspected on a percentage basis. Aring 220 to be selected or rejected is witnessed by a single angle lapoperation, under heavy lapping pressure. If the bottom side when lappingstarts is planar to at least about 10 light bands of flatness, then whenthe ring 220 is released from the fixture 46 the bottom side 238 willshow no high spots or low spots as witnessed. Such ring will belongamong the selected rings whereas others which become rejects will bewitnessed to be outside of the limits of flatness required.

It is not desirable and, in many cases, it is not necessary to haveinspection on single angle sealing sides of the rings. By 100%inspection is meant single angle lapping of every ring in a productionrun. It is even less desirable and in many cases unnecessary to have100% inspection of the double angle sealing sides of the rings. By 100%inspection is meant double angle lapping of every ring in a productionrun. Thus, within the skill of the art the ring control will be keptcareful, and so all unwitnessed rings will be used in engines and mostof the witnessed rings will be used because the rejects can reasonablybe expected to run few among witnessed rings.

At all events, the witnessed rings selected and the unwitnessed ringsare used in the same way in engine manufacture, e.g., in themanufacturing process of an engine provided with a number of cylindersand with that number of pistons individual to the respective cylinders,the pistons having compression ring receiving grooves presenting groovesides associated with the ring sides and being flat or substantially so.The process comprises: selection, from a plurality of split compressionrings, of rings for the grooved pistons having at least one side which,for its major portion in the free spring state of the ring, has aconsistent overall smoothness, which in the torsionally twistedcollapsed state with the ring closed or substantially so, has frustoconicity with the inner periphery of the side protruding and beingsubstantially coplanar at all points on the periphery, and which whenthe remaining major portion of the side is compressed into flattenedstate while so collapsed presents a substantially uninterrupted pressurering of face contact; sealing the pistons with such plurality ofcompression rings including such rings as so selected by installation ofa ring each in an associated compression ring groove on each piston withan associated side of the groove confronting the one side of the ring;and construction of the engines by assembling such pistons in therespective cylinders with each ring engaging a cylinder wall at alltimes to retain the ring in collapsed state on the piston. and with thering effective during the exhaust and suction strokes of engineoperation to establish a substantially continuous pressure ring of atleast line contact between the protruding inner periphery of said oneside and its associated confronting groove side to seal the piston, andduring the compression and firing strokes of engine operation toestablish a substantially continuous pressure ring of fully seated facecontact at the interface of the one side and its associated confrontinggroove side to seal the piston.

Broadly, the basic system here involved is to change from the casehitherto of having a good seal between ring side and groove side solelyas the exception or happenstance, and instead to make it the generalrule that the ring side and groove side have a substantially continuousring of face sealed contact when the ring is fully seated against theside of the groove.

Single angle lapping of the sealing side of a ring results in anuninterrupted major band which can readily be perceived visually by theinspector. If a double angle lap is used, as can be desired out of anabudance of caution, an uninterrupted narrow seal band results which canreadily be perceived visually. As a practical matter,

it has been found that when the narrow band exceeds 0.060 inch width atany point spaced from its ends, the ring is a proper subject forrejection. However, widening of the witness line width is permissiblewhen noted to occur within a fraction of an inch of the gap at the endsof the ring, because the line tends to widen materially at the gap.

The heavy lapping pressure required is materially less than maximumfiring pressure which will be encountered in the engine. A 100 lb. forceor several 100 lbs. of force for heavy lapping will be adequate,depending upon the size of the ring to be witnessed. A fraction of 100lbs. force has, for instance, been found inadequate in the case of acompression ring for a 4.3 inches bore engine. Specifically, a 35 lb.lapping pressure on the ring failed to flatten the sealing side againsta flat lap surface.

The light lapping pressure employed is from 1 to 4 lbs., and has noappreciable effect in deflecting the ring from its frusto conical lDseated, collapsed state.

We claim:

1. A process of manufacturing an engine provided with a number ofcylinders and with that number of ring grooved pistons individual to therespective cylinders, comprising the steps of:

selecting by means of a selection-rejection process from a plurality oftorsion type split compression rings, of rings for the grooved pistonseach having at least one side which, in the free spring state of thering, has a consistent overall flatness, which in the torsionallytwisted collapsed state with the ring closed or substantially so, hasfrusto conicity with the inner periphery of the side protruding andbeing substantially coplanar at all points on the periphery, and whichwhen the side is compressed into flattened state while so collapsedoperatively presents a substantially uninterruped pressure ring of facecontact; the one side during said face contact characterized by allpoints aforesaid thereof being planar to one another to at least aboutten light bands of flatness;

sealing said piston. with such plurality of compression rings includingsuch rings as so selected, by installation of a ring each in anassociated compression ring groove on each piston with an associatedside of the groove confronting said one side of the ring; and

constructing said engines by assembling such pistons in the respectivecylinders with each ring engaging a cylinder wall at all times to retainthe ring in collapsed state on the piston, and with the ring effectiveduring engine operation to establish a substantially continuous pressurering of at least line contact at the interface of said one ring side andthe confronting groove side associated therewith to seal the piston.

2. The invention of claim 1, the sealing of the pistons by rings incollapsed state characterized by twisting each ring in the associatedgroove with torsion during engine suction and exhaust thus tending torender said one side frusto conical, and characterized by tending tofully seat each ring in the groove with gas pressure during enginecompression and firing, causing a change in its sealing position from atleast line contact seating to substantially full face contact seatingagainst the side of the groove.

3. A process of manufacturing engines provided with a number ofcylinders and with that number of pistons individual to the respectivecylinders, said pistons having split compression rings andring-receiving grooves presenting groove sides associated with the ringsides and being flat or substantially so, said process com prising thesteps of:

selecting from a plurality of split compression rings,

of rings for the grooved pistons having at least one side which, for itsmajor portion in the free spring state of the ring, has a consistentoverall smoothness, which in a torsionally twisted collapsed state withthe ring closed or substantially so. has frusto conicity with the insidediameter corner of the side protruding and being substantially coplanerat all points, and which when the remaining major portion of the side iscompressed into flattened state while so collapsed presents asubstantially uninterrupted pressure ring of face contact with itsout-offlatness not exceeding about five or 10 light bands; sealing saidpistons with such plurality of compression rings including such rings asso selected by installation of a ring each in a ring-receiving groove oneach piston, with an associated side of the groove confronting said oneside of the ring; and constructing said engine by assembling suchpistons in the respective cylinders with each ring engaging a cylinderwall at all times to retain the ring in collapsed state on the piston,and with the ring effective during the exhaust and suction strokes ofengine operation to establish a substantially continuous pressure ringof at least line contact between the protruding inside diameter cornerof said one side and its associated confronting groove side to seal thepiston, and effective during compression and all firing strokes ofengine operation to establish a substantially continuous pressure ringof fully operating said engines whereby the associated confronting sideof the ring-receiving groove laps said knife edge flat in service so asto seal in narrow band contact and laps the seated face seal so as toretain it flat in service.

1. A process of manufacturing an engine provided with a number ofcylinders and with that number of ring grooved pistons individual to therespective cylinders, comprising the steps of: selecting by means of aselection-rejection process from a plurality of torsion type splitcompression rings, of rings for the grooved pistons each having at leastone side which, in the free spring state of the ring, has a consistentoverall flatness, which in the torsionally twisted collapsed state withthe ring closed or substantially so, has frusto conicity with the innerperiphery of the side protruding and being substantially coplanar at allpoints on the periphery, and which when the side is compressed intoflattened state while so collapsed operatively presents a substantiallyuninterruped pressure ring of face contact; the one side during saidface contact characterized by all points aforesaid thereof being planarto one another to at least about ten light bands of flatness; sealingsaid piston, with such plurality of compression rings including suchrings as so selected, by installation of a ring each in an associatedcompression ring groove on each piston with an associated side of thegroove confronting said one side of the ring; and constructing saidengines by assembling such pistons in the respective cylinders with eachring engaging a cylinder wall at all times to retain the ring incollapsed state on the piston, and with the ring effective during engineoperation to establish a substantially continuous pressure ring of atleast line contact at the interface of said one ring side and theconfronting groove side associated therewith to seal the piston.
 2. Theinvention of claim 1, the sealing of the pistons by rings in collapsedstate characterized by twisting each ring in the associated groove withtorsion during engine suction and exhaust thus tending to render saidone side frusto conical, and characterized by tending to fully seat eachring in the groove with gas pressure duRing engine compression andfiring, causing a change in its sealing position from at least linecontact seating to substantially full face contact seating against theside of the groove.
 3. A process of manufacturing engines provided witha number of cylinders and with that number of pistons individual to therespective cylinders, said pistons having split compression rings andring-receiving grooves presenting groove sides associated with the ringsides and being flat or substantially so, said process comprising thesteps of: selecting from a plurality of split compression rings, ofrings for the grooved pistons having at least one side which, for itsmajor portion in the free spring state of the ring, has a consistentoverall smoothness, which in a torsionally twisted collapsed state withthe ring closed or substantially so, has frusto conicity with the insidediameter corner of the side protruding and being substantially coplanerat all points, and which when the remaining major portion of the side iscompressed into flattened state while so collapsed presents asubstantially uninterrupted pressure ring of face contact with itsout-of-flatness not exceeding about five or 10 light bands; sealing saidpistons with such plurality of compression rings including such rings asso selected by installation of a ring each in a ring-receiving groove oneach piston, with an associated side of the groove confronting said oneside of the ring; and constructing said engine by assembling suchpistons in the respective cylinders with each ring engaging a cylinderwall at all times to retain the ring in collapsed state on the piston,and with the ring effective during the exhaust and suction strokes ofengine operation to establish a substantially continuous pressure ringof at least line contact between the protruding inside diameter cornerof said one side and its associated confronting groove side to seal thepiston, and effective during compression and all firing strokes ofengine operation to establish a substantially continuous pressure ringof fully seated face contact at the interface of the one side and itsassociated confronting groove side to seal the piston.
 4. The inventionof claim 3, such plurality of rings including rings whereof the insidediameter corner forms a knife edge initially sealing in line contact;and operating said engines whereby the associated confronting side ofthe ring-receiving groove laps said knife edge flat in service so as toseal in narrow band contact and laps the seated face seal so as toretain it flat in service.